Various therapeutic means are known for regaining tooth function which was lost by dental caries or periodontal disease. For example, a method for embedding an artificial tooth prepared from artificial materials such as metals or ceramics into the tooth root is known. Moreover, for example, if the loss is completely to the tooth root, a method for placing an artificial tooth while constructing a bridge between healthy teeth is known.
Further, oral cavity implant therapy has been conducted in recent years as one advanced therapeutic method of this dental substitution medical care. Oral cavity implant therapy is a means for setting an artificial tooth root such as titanium in the jaw bone of the site of lost tooth.
However, there is a significant difference between the tooth root of a natural tooth and a dental implant (artificial tooth root), in that the tooth root of a natural tooth is covered with periodontal membrane which is a part of the periodontium, whereas a dental implant transplantation site ordinarily does not have periodontal membrane.
Around at the natural tooth, there exist fibrous periodontal membrane tissue that connects the cementum on the tooth root side and the exterior alveolar bone. The cementum has the functions of protecting the tooth root surface and attaching the periodontal membrane to the tooth root surface. In addition, the periodontal membrane is known to have three functions broadly divided into: 1) an occlusal force cushioning effect, 2) a tooth migration ability (mechanics employed for orthodontic therapy and the like), and 3) a neurotransmission function of transmitting noxious stimulation (such as pain stimulation) such as occlusion and correction to the central nervous system. Among these, the periodontal membrane in particular has fibers running vertically to the longitudinal direction of the tooth root in order to cushion the occlusal force of teeth, and this running of the fiber in the periodontal membrane tissue is known to be an essential configuration for the functional expression of the periodontal membrane.
However, when a dental implant is transplanted, functional periodontium like those existing around the natural tooth cannot be formed at the implant transplantation site. For this reason, there was a problem with the dental implant transplantation site that absorption of the alveolar bone supporting the implant is caused by the occlusal force in long-term use, and it would no longer be able to withstand to use.
Accordingly, a technology that also enables the formation of periodontium similar to that of a natural tooth when a dental implant is transplanted has been long desired.
Until now, employment of periodontal tissue-derived cultured cells in order to allow formation of periodontium around the implant after transplantation has been investigated.
<Non-Patent Literature 1>
This literature discloses the utilization of progenitor cell-derived cultured cells collected from rat periodontal membrane. The literature discloses coating the implant treated with SLA with the cultured cells and Matrigel. The literature also mentions that periodontium was formed when this implant was transplanted to the tooth loss site of a rat.
However, the running of the periodontal membrane formed around the implant in the literature is parallel to the longitudinal direction of the implant, and differs from natural periodontal membrane. Since the running of periodontal membrane has an important meaning in supporting the occlusal force of teeth, a function to support occlusal force could not be expected with periodontium having such periodontal membrane.
<Non-Patent Literature 2>
This literature discloses a method of transplanting a titanium implant treated with EMD (Emdogain) to the jaw bone, and at the same time injecting PDL cells collected from the periodontal membrane into the transplantation site. This method uses a combination of agents with enamel matrix protein as the main component in order to attempt formation of periodontium around the implant. The literature also mentions the formation of tissue bound to the alveolar bone without epithelium tissue. However, the structure of the cementum which is one of periodontium is not observed in the periodontium formed. In addition, the running of a periodontal membrane in the periodontium is also not verified.
As such, a dental implant that enables the formation of functional periodontium has not yet been reported.